@es_kan
Cat girls are their own reason for existence. There is even a healthy population is pseudo-modern worlds. Because they are that cute.
Summoned or tamed monsters are a staple of fantasy, and actually come in many different forms, from cute mascots to huge beasts of destruction. The term "familiar" goes back to medieval stories about witches, who would have a demon in the form of an animal teach them magic as part of their bargain with unholy forces. In fantasy, any spellcaster's pet which isn't in the "giant monster" category is likely to be called a "familiar" regardless of the nature of their connection.
Disdain for single-class wizards? That's simple. Such people are supposed to be smart or even wise. They are hard to write.
It gets even worse when the wizard has magic that is good for more than just blasting opponents.
That said, try reading Kuma Kuma Kuma Bear and Magi Craft Meister. Their protagonists are very much wizards.
@Goldenzeal - I am up to date with WN translation, no reason to give me spoilers.